Fluid-fuel-fired boiler



B. GREENFIELDJ FLUID FUEL FIRED BOILER Nov. 11, 1930.

Original Filed March 12 1920 Patented Nov. 11, 1 930 UNITED STATES BENJAMIN PATENT OFFICE GREENFIELD, OF NEW YORK, N. Y., ASSIGNOR-TO DOHERTY RESEAZkCH COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE I FLUID-FUEL-FIRED BOILER Continuation of applicationserial No. 365,366, filed March 12, 1920. This application filed August 5,

1926. Seria1N0.127,351.

This invention relates to fluid fuel fired boilers, and more particularly to a device for automatically controlling. the supply of fuel and air to oil and gas fired boilers.- The 5 present invention wasoriginally described in my application, Ser. No. 365,366, filed March 12. 1920, of which this is a continuation.

With the rapid development of fluid fuels (oils and gases for instance) for industrial purposes, the combustion efficiencies obtained in burning these fuels havebeen extremely low. This has been due mainly to the fact that fluid fuels have been used in furnaces which are not properly constructed for such combustion.

caused principally by overventilation, but losses may also occur from'underventilation. The underventilation loss is caused by an insuflicient supply of air for the fuel so that 2 the unburned products pass out of the stack with the flue gases. The common and largest loss is caused by overventilation in which an excessive amount of air is usedto burn the fluid fuel, thereby giving a decreased flame temperature and causing a very large amount of heat to be carried out of the stack with the flue gases.

To obta n the highest efliciency in the combustion of oil and gas, it is necessary to supply the fluid fuel and air for supporting com-- bustion in such proportions that the air will just suflice. to completely burn the fuel and will not be in sufficient excess of this amount to materially cool the flame or dilute the hot products of combustion. Because of the small volume of fluidfuel used, the proper proportioning of the fuel and .air requires great accuracy in their control and measurement, since a comparatively large variation from the 4 proper proportions of fuel and air is caused by a comparatively small excess or deficiency in the volume of fuel above or below that required for perfect combustion.

This accuracy of control of the volume of oil supplied can not be obtained by varying the opening of the control valvescommonly used on the oil supply pipe, since the flow through these valves does not follow any definite law. This is more especially the case when the volume of oil is constantly or The fuel losses are.

frequently varied with changes in the con- Under sumption of steam from the boiler.

accurately measured, nor can the measurement be accurately transmitted to an a1r su pply controlling device. It has, therefore,

been customary to supply air in a substantially constant volume and in excess of that required for perfect combustion in order to insure complete combustion during the largest fuel supply. Consequently, a large part of the heat of combustion is wasted in heating this excess of air rather than used in generating steam or for other'useful work.

The primary'object of the present invention is to provide a method of controlling combustion of' fluid fuel by which the proper amount of air to support complete combustion is supplied to the furnace at all rates'of supply of fuel.

Another object of the invention is to provide an apparatus by which the air supplied to oil and gas fired furnaces will be just sufficient to complete combustion at all rates of supply of fuel.

The rate of combustion in gas and oil fired boiler furnaces may be widely varied substantially instantaneously and may be forced at times past the limits at which good combustion efficiencies may beobtained. In addition to disturbing the conditions governing combustion, sudden variations in the rate of combustion with consequent sudden over-heating and cooling of the furnace have an injurious effect on the boiler settings, due to rapid expansion and contraction. This is more especially the case when a battery of several boilers is used to supply a variable demand for steam and when the load may be unevenly distributed so that the variation in load, and

consequently in the rate of combustion, falls principally on'one or on only a part of the boilers of the battery.

Accordingly, a further object of the inven-' of combustion in all of the furnaces of a battery of boilers will be substantially equal.

A further object of the invention is to provide an apparatus for governing the rate of supply of oil or gas to boiler, furnaces in which the rate of supply of fuel will correspond to the steam consumption at all boiler loads.

In many localities, especially where natural gas is obtainable, it is customary to use both gas and oil as their market prices vary, the cheapest one being used as fuel. In some cases, gas is used where available because of its cheapness and convenience, and oil is used when the supply of gas fails, the furnaces being arranged to burn either oil or gas. The change from one fuel to the other makes the control or regulation of combustion much more diflicult than in the case where either oil or gas alone is used because of the difference in heating value and in the quantity of air required for complete combustion ofequal volumes of the two fuels.

A further object of the invention is, therefore, to provide an apparatus capable of automatically controlling the combustion of both gas and oil in a furnace. 7

With these and other objects in view, the invention consists in the method and apparatus described in the following specification and defined in the claims.

The various features of the invention are ilgiven pressure to a definite consumption ofsteam, Thus, the limits may be fixed at 200 4s pounds pressure when no steam is being used,

and at 190 pounds for full load, the pressures intermediate these limits corresponding to fractions of full load steam consumption. The controlling device for the air and gas or oil is arranged to supply fuel and air in amounts suflicient to generate steam equal to the load demand. Thus, when the steam consumption equals 60% of a'full load, the steam pressure willbe, say, 194 pounds and'the fuel supply will be 60% of that required for full load conditions. .If the load increases to 100%, the steam pressure will drop to 190 pounds and the fuel supply will increase with the drop in steam pressure until the full load "conditions are obtained. If the demand for steam ceases the steam pressure inthe'boiler y, will gradually buildup and the fuel supply willcontinuously decrease until a'pressureof pounds is produced, at which fuel supplyis at a It 1s not espoint. the

being used, the gas supply pipe is provided with a regulating valve which is always under the control of the steam pressure in the boiler. As the consumption of steam decreases, the pressure in the boiler builds up and moves the valve towards closed position, thereby decreasing the supply of fuel to correspond to the decreased load. When the consumption of steam increases the boiler pressure falls since the fuel supply is not sufiicient to generate the increased amount of steam. The gas supply valve is thereby opened and the fuel supply increased to correspond to the decreased steam pressure.

When oil is being used as a fuel, the supply of oil is similarly controlled by the steam pressure of the boiler. Inasmuch as the volume of oil is much smaller than the'volume of gas required for a given load, and because of the difficulty or impossibility of determining the flow of oil. through control valves with sufficient accuracy, the oil isv caused to pass through a standard orifice under a definite drop in pressure. The rate of flow of the oil is controlled by controlling the pressure or difference in pressures under which it is forced through the orifice. The

pressure on the oil is very accurately controlled by the continuous admission to and escape from the oil of a regulated amount of gas under pressure. For this purpose, gas from the gas supply. main is conducted through a steam controlled valve to an oil feeding device provided with an oil out-let orifice through which oil is fed to the boiler. A small amou t of gas is always allowed to escape from th oil feeding system through an. escape outlet so thatthe gas pressure in the oil feeding device is at all times dependent on the rate of admission of gas from the gas supply main. As the steam pressure in theboiler rises and closes the valve, the pressure on the'oil supply system is decreased through a gradual escape of gas through the escape outlet and as the boiler pressure decreases, gas is admitted through the control valve faster than it can escapelthrough the escape opening until the pressure builds up and the rate of oil supplied through the standard orifice increases proportionately.-

The volumes of-oil and of gas supplied under a given pressure are different but are so proportioned that the same quantity of air will'be required for complete combustion of the gas and oil supplied under any given pressure. A common damper control, governed by the pressure at which gas 15 supplied to the furnace, or the pressure at which the oil is forced throughthe standard orifice when oil is being burned,'is used for controlling the draft of air to the furnace. Since the flow of oil or gas does not vary directly as the pressure differential through the flow controlling orifice but varies as the square root of this pressure differential, in accordance with the we'll-known law of the flow of fluid through an orifice, the damper controlling device is so arranged that the area of the damper opening will increase approximately in direct proportion to the pressure differential controlling flow of oil or gas. Furthermore, the flow of the products of combustion through the stack damper opening will naturally vary as the area of the opening, and therefore by the above arrangement the rateof the feeding of the air to the furnace will vary approximately as the rate of the.

feeding of the fuel to the burner. Through this arrangement, the firing of the furnace may be quickly changed from oil to gas or vice versa, and the proper quantity of air will be supplied in both cases without requiring any adjustment in the damper-com trolling apparatus.

Referring to the accompanyin drawing, gas is supplied to a'furnace 10 from a gas supply main 12. The gas from the main 12 is brought to a constant low pressure by a constant pressure regulator 14 and any accidental increase in pressure after passing the regulator 14 is prevented by a pressure safety device 16. From the pressure regulator the gas flows through a gas meter 20 and through a controlling valve 22 to burners-24 in the boiler furnace 10. The passage of gas through the controlling valve 22 is controlled directly by the steam pressure in the boiler 10 so that at any given boiler-steam pressure a definite amount of gas flows through the valve.

For this purpose the position ofthe valve 22 is governed by a diaphragm 26, one side of which is in communication with the steam .lome of the boiler through a connecting pipe 28. As the'steam pressure in the boiler increases it tends to depress the diaphragm 26 to close the valve 22. The closing action of the steam is opposed by a weighted lever combustion in the furnace 10 is controlled by a damper 34 in a stack or flue 36 of the furnace in such a manner that the opening for the passage of exhaust products of combustion will. be approximately proportional to the rate of flow of gas or oil. Tothis 'end the damper 34 is rigidly mounted on a rotatable shaft 38 the position of which is so governed by the pressure of the fuel gas passing to the burners 24 that the rate of flow of gases past the damper is approximately proportional to the square root of the fuel gas pressure. The pressure of the gas passing from the'valve 22 to the burners 24 is transmitted through branch pipes 40 and 42 to a vertically mov-. able gas bell 44. The gas-bell 44 is positioned within a tank 46 which is partly filled with water or other liquid to seal its lower end, The weight of the bell 44 is supported partly by the pressure of the gas within the bell and by the rising of the bell' 44 is assisted by a .flow of the gas entering the burners 24, and

the shaft 38 is rotated to lower the Weight 52, the moment arm of the weight 54 on the shaft 38 decreases and is proportional to the sine of the angle made by the crank arm- 56 with the vertical. Since the pressure in'the bell 44 must be inversely proportional to the moment, arm of the weight 54 in order to have an equilibrium of forces, the damper 34 continues to open as the pressure in the bell increasesuntil the dampercomes to full open position. It has been found thatwith this arrangement the quantity of gases passing through the stack 36 and accordingly ,the air admitted to the furnace vary approximately as the square J root of the gas pressure-transmitted to the bell 44 and is therefore proportional to the rate of supply of oil or gas to the furnace. The pressures which may be used in the bell 44 to move the damper from closed to fully open position may be varied by adjusting the position of the Weight54 on the arm 56 or by varying the weights 52 and 54.

When oil is being used as a fuel, the admis-v sion of gas to the burners 24 and to the bell 44 is prevented by closing valves 58 and 60 in the pipes 12 and 40 respectively. A supply of oil is then forced from a feed tank 62 through a connecting U-tube 64 to an overflow tank 66. A standard orifice 68 is positioned at the end of the tube 64 which is located in the overflow tank 66. From-the-tank 66 the oil flows into an oil feed pipe 70 leading to an oil burner 72 preferably of the steam injection type, in the boiler furnace 10.

The rate .at which oil is fed from the oil feed tank 62 to the overflow tank 66 is indirectly controlled by the steam pressure in the boiler 10. To this end, a small amount of gas is taken from the gas supply main 18 through a branch pipe 74 and passes through a steam controlled valve 76 to a pipe 78 lead ing to the top of the oil feed tank 62. The pipe 78 is provided with an escape outlet 80 through which a small amount of gas may continually escape, Since all of the gas passing through the valve 76 must escape through the outlet 80, the pressure in the pipe 78 is dependent upon the rate of admission of gas through the valve 76, as the rate of escape of gas through the outlet 80 is a function of the pressure in the pipe 7 8. The opening of the valve "76 is controlled by a diaphragm 82 which communicates with the steam chamber ofthe'boiler 10 through a branch pipe 84. As the pressure in the boiler increases, it tends to force the diaphragm 82 downwardly and close the valve 7 6. The downward force exerted by the diaphragm 82 is opposed by a weighted lever 86 which tends to open the valve 76. Theweight on the lever 86 is so adjusted that the valve 6 will be open at all pressures below a certain minimum, say 190 pounds, and as the pressure increases slightly above 190 pounds, it will overcome the weight of the lever 86 and move the valve 76 towards closed position. The valve 76 is prevented from moving to a fully closed position at pressures slightly above 190 pounds by a spring 88 attached to the weighted lever '86 and arranged to exert an increasing force as the lever is raised. The tension of the spring 88 s so adjusted that the valve 76 will not be fully closed until the boiler pressure reaches a definite maximum, say 200 pounds. At all pressures between these limits,.the valve will be opened a distance' corresponding to the steam pressure of the boiler and accordingly the gas pressure which is built up in thepipe 78 and tank 62 will have a definite relation to the steam pressure in the boiler.

Means mechanically the equivalent of the spring'88 may be employed for giving a par- 1 tial. opening of the valve' at pressures between the maximum. and minimum limits. The gas pressure in the pipe 78 may be meas fured by a manometer 90 and recorded bya recording device 92. The record' 'ofthe gas pressure by the recorder 92 will give an indication of the quantity of oil burned.

In order that the flow of oil through the orifice 68 may depend entirely on the gas pressure transmitted through the pipe 7 8, a a constant level of oil is maintained in the oil-feed tank 62. For this purpose the tank 62 is divided into two compartments 94 and 96 by a partition 98 of the same height as the overflow pipe 70 and oil from a storage tank 100 is forced by a pump 102 into the compartment 94 and caused to flow over the partition 98 into the compartment 96. From the compartment 96 the oil returns to the tank 100 through a return pipe 104.

It will be readily appreciated that the pipe I 70 constitutes in eifect an oil standpipe or supply pipe from the foot of which oil flows to the burner 72. and that the, head of oil in the v standpipe depends on the rate of feed of oil from the constant level compartment 94 of tank 62 into tank 66 through the orifice68, the rateof feed therefore primarily depending on the boiler steam pressure. It

will be understood, therefore, that as the boilersteam pressure falls the supply of oil to the tank 66 increases, thereby increasing the head of oil in the standpipe 70 over the burner 72 and supplying'a greater volume of oil to the burner. 1 I The .rate at which oil passes through the orifice 68 depends onthe pressure in the tank 62; Therefore the amount of oil passing through the orifice 68 follows the well-known equation 10 in which Q, is the quantity of oil passing through the orifice, c the orificecoeflicient, a the orifice area, 9 the gravity co- 105 eificient, and h the pressure acting on the oil. Therefore the quantity of oil passing through the orifice is proportional to I the square root of thepressure in the pipe 78. The pressure in the pipe78 is, also, used to control the position of the damper 34 when oil is used as a fuel. For this purpose. pressure from the pipe 7 8'is transmitted through a branch pipe 106 to the pipe 42 leadingto the bell 44 and operates the bell 44 and damper 34 in substantially the same manner as the gas pressure transmitted through the pipe 40.. The size of the orifice 68 is so adjusted to the gas burning system and to the damper controlling device that the same quantity of air will be required for complete combustion of the oil or gas when the gaseous pressure transmitted through pipes 106 and 40 are the same. No

adjustment of the draft controlling mecha- 1 5 In adapting the apparatus for burning oil in the furnace, use has been made of combustible gas for controlling the feed of oil to the burners. It is not necessary to use gas for this purpose, but substantially any fluid medium which is available at auniform pres sure may be used in the place of gas. For example, compressed air under uniform pressure may be introduced into the plpe 74 or steam under uniform pressure may be introduced in the pipe '74. when gas is used as a controlling medium, the amount of gas passing through the escape outlet is comparative 1y small and this may be burned directly at the outlet. In case it is found desirable to allow a comparatively large amount of gas to pass through the outlet 80, the gas passing through the outlet may be conducted to the boiler furnaces.

The supply of oil from the tank 62 may be independently controlled by means of a pilot pipe 112 leading from the branch pipe 74 to the furnace 10. A valve 114 is'mounted in the pipe 112, and when this valve is open all of the gas admitted through the valve 108 in the pipe 74 will flow through the pilot pipe and reduce the pressure in the pipe 78 to such a point that little or no oil will be forced through the orifice 68. In some cases, and especially Where the installation is used for heating oil stills and similar apparatus which are run at substantially atmospheric pressure and in which therefore the controlling valve 76 cannot be used, the supply of fuel may be controlled manually by the valve 114. When, therefore, the rate of combuS-.

tion of oil inthe furnace is to be decreased, the valve 114 is opened, thereby shutting off the supply of oil and simultaneously admitting a small amount of gas through vthe pilot pipe 112. \Vhen the rateis to be increased,

the valve 114 is closed, thereby cutting off the supply of gas through the pilot pipe 112 and building up the supply of oil through the -orifice 68. The draft control operates however, through the branch pipe 106 in the same manner as in the case when the control valve Lil 76 is employed. The escapeoutlet 80 is closed bya valve 117 when thepilot pipe 112 is being used and the pilot flame burns contin- 'uously, the size of the flame depending upon as the boiler steam pressure decreases the heat energy stored in the boiler is utilized in helping to supplying the increased demand for-steam. This in turn operates to make the necessary changes in rate of combustion less violent, with a resultant increase in com bustion efliciency and longer life of furnace linings.

The system also permits of properly proportioning the load between any number of units of a battery of boilers even though the boilers may be of varying capacity. Each boiler thus not only takes at all times its proper share of the load, but also takes its proper share of the fluctuations in load, there.

'by contributing very materially to better combustion efficiencies and low boiler and furnace maintenance as compared with plants Where a part of the boilers may be operated at a constant rate and a small part of the boilers in service be required not only to take care of all variations in load on the plant but also attempt to maintain a constant steam pressure on the main steam header.

By providing aseparate orifice similar to 68 for each boiler furnace, proportioned in size according to rated capacity of the boiler and allowing its discharge to go into a separate compartment in chamber 66 and thence to the proper-boiler furnace and burner by means of an overflow pipe similar to pipe 70, it is possible to .supply several boiler furnaces from a common feed tank 62 with the use of butone pressure controlling apparatus.

The oil is thus proportionally distributed to.

70 is Withdrawn through a branch pipe and I another orifice similar to 68 in a second compartment of 66. From the second compartment it is then conducted through an overflow pipe .similar to 70 directly to pipe 118 and to the furnace of a second boiler 119, the boilers 119 and 10 being connected by a common steam main 120. The draft through the furnace of boiler 119 is controlled by a damper 121 which is in turn governed by a bell122 arranged similarly to the damper 34 and bell 44 of the boiler 10. The position of the bell 122 is controlled by means of the gas pressure admitted from the pipe 78 through a branch pipe 124. By means of this arrangement the amount of gases flowing past the damper 121 is at all times proportional to the amount of oil supplied through 118 to the furnace of the second boiler. Similarly the branch pipe 126 conveys gas from the supply pipe 12 and a branch pipe 128 transmits pressure from the pipe 126 to the bell 122.

A pilot pipe 130 common to both boilers is provided to convey a small amount of oil from the tank 66 to the furnaces of boilers 10 and 119 to feed a pilot burner during periods when the. supply of oil or gas is completely shut off from main burners. The feed p1pe 70 is also providedwith a drain pipe 132 leading to the tank 100 through which the pipe 7 0 may be emptied when not in use.

The pipe feeding the second boiler furnace is drained by similar means.

Because of the accuracy with which the flow of oil through the standard orifice may be restricted and controlled, and of the responsiveness and sensitiveness with which the pressure of the gas used to force the oil through the orifice may be transmitted and restricted,-the apparatus is capable of maintaining under all boilerloads the proper rate of combustion and the conditions favoringIthe highest combustion efficiencies. aving described the preferred form of the invention, what is claimed as new is 1. In a fluid fuel fired boiler the combination of means for feeding fuel to the fur- 'nace of said boiler under a gas pressure controlled by the steam pressure in said boiler and means controlled by the pressure of said gas for controlling the draft damper of said boiler furnace. I

2. In a fluidfuel fired furnace the combi nation of means forsupplying fuel oil to the furnace, a flow restricting :device in said oil supply means, means for supplying gas under pressure to force oil through said device, a draft controlling damper for said furnace, and means governed by the pressure of said gas for controlling the position of said,

damper. I

3. In combination with a battery of boilers havlng their steam spaces connected, of

an oil supplychamber provided with outcontinuously supplying gas under pressure to'such chamber, an outlet for the gas supplying means arranged to'continuously permit gas to escape to control the pressure in the chamber, and an outlet for oil from said chamber having aflow controlling device.

5. A combustion regulator for fluid fuel fired-boilers comprising an oil feed chamber, means governed by the steam pressure of said boiler for placing said chamber under gas pressure, an escape outlet for said gas, an oil outlet from said-chamber having an orifice, a damper for the furnace ofsaid boiler having an adjustable weight rigidly mounted on its. shaft at a distance from its axis, a pulley on said} dam-per shaft, and a gas bell communicating with the gas space of said oil feed chamber, and arranged to rotate said pulley.

6. A combustion regulator for fluid fuel fired boilers comprising an oil feed chamber, means governed by the steam pressure of said boiler for placing said chamber under gas pressure, an escape outlet for said gas, an oil .outlet from said chamber having a regulating orifice, a damper for the furnace. of said boiler, and means for opening said damper a distance substantially proportional to the flow of oil through said orifice.-

7. A combustion regulator for fluid fuel fired boilers which comprises an oil feed chamber, an outlet for said chamber having a regulating orifice, an oil feed pipe leading oil delivered by said orifice to the furnace of said boiler, and means for generating different pressures in said oil feed tank for every boiler steam pressure between definite limits. l

8. A combustion regulator for fluid fuel fired boilers which comprises an oil feed chamber, an outlet for said chamber having' a regulating orifice, an oil feed pipe leading oil delivered by said orifice to the fur-- nace of said boiler, means for generatin a definite pressure in said oil feed cham er for every boiler steam pressure between definite limits, and means governed by the pres sure in said oil feed chamber for control-- ling the draft to said furnace.

9. The method of regulating combustion in fluid fuel fired furnaces which comprises conductinga'flui'd fuel stream to,the furnace through a constant area flow-restricting orifice, developing a low pressure differential across the-orifice to cause fuel to flow therethrough, and at intervals reducing the pres sure dropacross the orifice substantially to zero and automatically restoring the pressure differential to substantially sus end and. au-

tomatically resume the feed 0 fuel to the orifice tocause fuel to flow therethrough, and

means operable to reduce the pressure drop across the orifice substantially to zero and to automatically restore the pressure difl'erentialso that the'flow of fuel to-the furnace may be substantially suspended and automatically resumed.

11; In aifluid fuel fired furnace, the com- 125,

bination of an oil supply container, an ori-.

means Afor admitting fuel gas at a limited rate't'o said oil container, means for permitting the escape of fuel gas from said container at a limited rate, and a valve controlled pilot pipe connecting the gas space of said oil container to said furnace. I

12. In a fluid fuel fired boiler, the combination of a gas supply pipe, means controlled by steam pressure for governing the rate of supply of gas to the furnace of said boiler, a damper controlling the draft of said furnace and having a weight rigidly mounted on its shaft at a distance from itsaxis, a

pulley on said damper shaft, a weighted cagas in said oil container, a damper for the furnace ofsaidboiler having a weight rig-' idly mounted on its shaft, a weighted cable passing over said pulley, a bell attached to said cableand having a liquid seal at its lower end, and means for subjecting the interior of the bell to the'same pressure as that in said oil container.

14. In afluid fuel fired boiler, a closed container for oil, an outlet for oil from sai container having a flow controlling orifice, means for placing said container under gas pressure, means governed by the steam pressure in said boiler for controlling the pressure of. gas in said oil container, a damper for'the furnace of said boiler, and means controlled by the same pressure as that in said oil container for governing the opening of said damper.

15. In a fluid fuel fired furnace, the com-- bination of a closed container for oil, an outlet for oilfrom said container having a flow controlling 'orifice, means for placing said container under gas pressure, a damper for the furnace, and means governed by the same pressure as the pressure of gas in said oil container'for controlling the opening of said damper.

16. The'combination 'witha fluid fuel fired furnace of a' closed container for oil, means for maintaining a constant level of oil in said container, an outlet for oil from said container'having a flow controlling orifice, means for placing said container under gas pressure, a damper for the furnace, and means governed by the same pressure as the pressure of gas in said oil container fdr con trolling the opening of. said damper.

. Y 17 In a fluid'fuel fired boiler furnace having separate oiland gas burners, the combina-y tion of a gas supply pipe. for said furnace,-

a valve in said supply pipe controlled by the steam pressure of the boiler, an oil container, an outlet from said oil container having a measuring orifice, a conduit leading from said orifice to said oil burners, a branch pipe 7 leading from said gas supply pipe to said oil container, .an escape outlet from said branch pipe, a damper for said furnace having a weight rigidly mounted on its shaft at a distance from its axis, a pulley mounted 7;

on said shaft, a weighted cable running over said pulley, a Water sealed bell connected to said pulley,'and means for selectively transmitting gas pressure from said oil container or from the inlet to said gas burners to said o bell.

18. In a fluid fuel fired steam boiler the combination of a gas supply pipe, a valve in said pipe controlled by the steam pressure of said boiler, a closed oil container, an outlet from said oil container having a flow controlling orifice, a conduit for leading oil delivered by said orifice to a burner in the furnace of said boiler, a branch pipe leading from said gas supply pipe to said oil container, -.an escape outlet from said branch pipe, a steam controlled regulating valve in said branch pipe, a damper for said furnace,

and means controlled independently of the 1 pressure in said branch pipe by a pressure 05 derived from the pressure of gas in said gas supply pipe for controlling the position of said damper;

'19. Ina fluid fuel fired furnace the combination of a gas supply pipe, a closed oil conloo tainer, an outlet for oil from said'container having a flow ontrollingorifice, a conduit for leading'oil delivered by said orifice to an oil burnerin the furnace, a branch pipe from said gas supply pipe to said oil .con-

tainer, an escape outlet communicating with said oil container, aregulating valve in said. branch pipe, a damper for said furnace, and means controlled independently of the pressure injsaid branch pipe by a pressure derived 1 H) from the pressure of gas in. said gas supply pipe for controlling the opening of said damper.

20. In a'fluid fuel fired furnace, the combination of a gas supply pipe, an oil con- H5 tainer, an'outlet for oil from said container: having. a flow controlling orifice, a conduit leading oil delivered by said orifice to oil burners in the furnace, a branch pipe leading from'said gas supply pipe to said oil con- H0 tainer, a throttle valve controlling the admission of gas to said branch pipe, a pilot tube from said branch pipe to said furnace,

a' controlling ,valve in said pilot tube, a

.damper' for said furnace, and means gov- 21. A method of controlling combustion in oil fired boiler furnaces which comprises, conducting oil to the furnace of said boiler with a gravity feed, supplying oil to the feed through a constant area restriction by means of a low gas pressure, and controlling the pressure of the gas by the steam pressure of the boiler.

22. A method of controlling combustion in oil fired furnaces which comprises, maintaining'a body of oil, developing a gas pressure on the oil body to remove oil at a definite rate therefrom, conducting the oil-removed from the body to the furnace by gravity, supplying air to the furnace, and controlling the supply of air to the furnace in accordance with the gas pressure maintained on the said oil body.

2. A method of controlling combustion in oil fired boiler furnaces which comprises permitting the steam pressure in said boiler to vary with variations in the load on the said boiler, maintaining a body of oil, devel-. oping a gas pressure on the oil body to remove oil at a definite rate therefrom, conducting 5 the oil removed from said body to the furnace by gravity, and varying the gaseous pressure on the oil body in accordance with the variations of the steam boiler pressure.

24:. A method of controlling the fuel supplyto a battery of boiler furnaces which comprises permitting the pressures in said boilers to vary in accordance with the load on the battery, maintaining a body of fluid fuel for supplying the furnaces of the battery, developing a gas pressure on the oil body which is inversely proportional to the steam pressure on one of the saidboilers, leading oilremoved from the body to the individual boiler furnaces, and proportioning the oil 40 supply between the. individual furnaces of the battery.

' 25. A method of controlling combustion in a battery of boiler. furnaces which com prises permitting the pressures in said boilers v4.5 to vary with the load, controlling the supply of fuel to said battery indirectly by the steam pressure of one boiler, proportioning the 011 supply between individual boiler furnaces of the battery, and transmitting the pressure under which oil is supplied, by means of a gaseous medium, to draft controlling dampers on said boiler furnaces.

26. The method of controlling combustion in an oil fired boiler furnace which com- 5 prises supplying gas at a slow rate to a body of oil, causing said oil to flow to said boiler furnace at a rate governed by the pressureof ,said gas upon the oil, and substantially instantaneously and completely releasing the 6 pressure on said body of oil when the steam pressure in the boiler reaches a definite maximum.

27. A method of controlling combustion causing said oil to flow to said boiler furnace at a rate governed by the pressure of said gas, releasing the gas pressure on said body of oil when the steam pressure in said boiler reaches a definite maximum, regulating the gas pressure on said body of oil and supplying air to said boiler furnace at a rate proportional to the square root of the gaspressure-on said body of oil.

28. A method of regulating combustion in a furnace which comprises, maintaining a body of fuel at a constant level, conducting fuel from said body to a burner in the furnace through a conduit provided with a constant area flow restriction, supplying fuel to the burner by developing a low fluid pressure on the fuel body suflicient to force'the fuel through'the flow restriction, and varying the flow of fuel through the restriction between zero and a desired maximum solely by control of the pressure on the fuel body.

29. A method of regulating combustion in an oil fired furnace which comprises forcing a supply of oil'through a flow restricting device to a burner for the furnace under a' low pressure arbitrarily developed in accordance with the character of the burner, limiting the maximum pressure which may be developed for forcing oil through said flow restricting device, and controlling the furnace draft in accordance with the pressure employed for feeding the oil.

30. A method of regulating combustion in a fluid fuel fired boiler furnace which comprises feeding a fluid fuel stream through a.

flow restricting orifice to a burner in said furnace, developing a fluid pressure uniformly and substantially less than boiler steam pressure for controlling the flow of fuel through the orifice, and varying the fuel feeding pressure in inversely proportional relation with variations in the pressure .of steam in the boiler. v

31. A method of controlling combustion in a fluid fuel fired boiler furnace which comprises. maintaining a body of oil. conducting oil fromthe body to a burner in the furnace, developing a low pressure on the oil body to force oil to the burner, restricting the oil flow to the burner by a constant area orifice, supplying air to the furnace, controlling the air supply by mechanism operated directly by the oil feeding pressure. and varying the oil feeding pressure in accordance with variations in the steam demand on the boiler.

32. In a fluid fuel fired boiler the combination of means for feeding fluid fuel through a flow restricting orifice to the furnace of said boiler, means for automatically proportioning the rate of flow of fuel fed I to the furnace in accordance with the steam. demand on the boiler, a draft controlling damper for said boiler -furnace,. and means for varying the area of opening said damper proportionately with variations in the rate of ow of fluid fuel through said orifice.

33. A combustion regulator for oil fired boiler furnaces which comprises an oil burner, a flow restricting device for delivering oil to said burner, means for developing a low pressure upon oil passing through said device, means for limiting the pressure which may be developed on the oil, and means governed by the steam boiler pressure for varying the oil feeding pressure.

34. A combustion regulator for oil fired furnaces which comprises an oil burner, a closed oil container, means 'for conducting .oil from the container to the burner through a flow restricting device, means for developing a low pressure for forcing oil through said device, means for limiting the pressure which may be developed upon the oil passing through said device, a draft control damper, a motor for operating said damper, and connections between said burner feeding device and said motor whereby the pressure developed for feeding oil will operate the damper motor.

35. A combustion regulator for 'fluid fuel fired boiler furnaces which comprises means for supplying fuel to said boiler furnace under a low pressure at a rate inversely proportional to the steam boiler pressure between definite limits thereof, means for admitting air to the furnace, and means for controlling the draft through said boiler furnace to maintain a rate of air supply substantially proportional to the square root of the pressure used in feeding fuel.

36. Acombustion regulator for fluid fuel fired furnaces comprising a burner, means for feeding fuel tothe burner including a member equipped with a flow restricting orifice of constant area through which a fluid fuel stream is fed, means for producing a low pressure differential across the orifice, and means operable to reduce the pressure drop across the orifice substantially to zero and to restore the pressure differential to substantially suspend and automatically resume the flow of fuel. to the burner, said feeding means 1 being operable to maintain a fiow of fuel through the orifice whenever there is a greater pressure on the supply side than on the delivery side of the orifice.

37. A combustion regulator for a fluid fuel fired furnace comprising a burner, and means for feeding a fluid fuel stream to said burner including a member provided with a restricted opening of constant area and substantially uniform dimensions on two ma or ages intersecting at right angles through which the fluid fuel stream is fed,'=means for delivering the fuel to the supply side of said opening, means for developing a fluld pressure differential across the opening to force fuel therethrough, and means operable to reduce the pressure drop across the opening communicating with said plate on its delivery side, means for exerting pressure on the fuel in the first chamber, and means for conduct- I ing fuel under gravity head from the delivery side of'the orifice to the burner.

39. A combustion regulator for fluid fuel fired furnaces including a burner and means for feeding a fluid fuel stream to the burner including a chamber, means for maintaining the fuel in said chamber at a predetermined level, a pipe communicating with the chamberbelow the level of fuel therein and extending upwardly, a second chamber enclosing the other end of the pipe and open to the atmosphere, an orifice plate arranged to communicate on its supply side with the pipe and on its other side with the second chamber,

, means for conducting fuel by gravity from the second chamber to the burner, and means for imposing gaseous pressure greater than atmospheric on the fuel in the first chamber to;induce flow of. fuel to the burner.

40. A method of controlling combustion in a fluid fuel fired boiler furnace which com prises permitting the steam pressure in said boiler to vary with variations in the steam demand on the boiler, feeding fuel to the furnace at a rate which varies in accordance with variations in the steam demand on the boiler, and supplying air for supporting combustion to the furnace at a rate which varies proportionately with variations in the steam demand on the boiler.

41. The combination with a'boiler furnace having two fuel burners mouted therein, of means for feeding fuel to each of said burners, means for supplying air to the furnace for the combustion of said fuel, mechanism for accurately proportioning the air supply in accordance with the rate of flow of fuel fed to the burner, and mechanism governed by boiler steam pressure for proportioning the fuel supply in accordance with the steam demand on the boiler.

42. The method of operating a fluid fuel burning-furnace which consists in supply- 'the fluid fuel to the furnace chamber to be burned therein, supplying air to the furnace chamber for combustion, and regulating the super-atmospheric pressure head, supplying air for combustion to the furnace, and regulating the combustion in accordance with the rate of supply of said element of combustion to the furnace.

45. The method of operating a fluid fuel fired boiler furnace which consists in supplying an element of combustion at a constant super-atmospheric pressure head, supplying another element of combustion to the above the burner which increases in proportional relation with the rate that oil is supplied thereto, and feeding oil to the burner under the head of oil in the standpipe.

In testimony whereof I aflix my slgnature.

, BEN J AMIN GREENFIELD.

furnace and regulating the combustion in accordance with the rates of supply of said elements of combustion to the furnace.

- super-atmospheric pressure, supplying an and varying the rates of supply of both of said elements of combustion to the furnace 1n lnverse proportlonal relatlon to variations 46. The method of operating a fluid fuel fired boiler furnace which consists in supplying an element of combustion at a constant other element of combustion to the furnace,

in the boiler-steam pressure.

47 In a fliel-oilfeeding device for a boiler furnace, the combination with a burner through which fuel is supplied to the furnace, of an oil supply pipe extending upwardly from the burner, and means for increasing the head of oil in the suppl pipe in proportional relationwith the f all of steam ressure in the boiler.

48. n a fuel-oil feeding device for aboiler furnace, the combination with a burner through which the fuel is supplied vto the furnace, of an oil standpipe extending upwardly from the burner, and means for increasing the head of oil in the standpipe in proportional relation with the fall of steam pressure in the boiler, said means including "a chamber containing oil under a constant head, a conduit leading from said chamber to the standpipe, and means for exerting a boiler pressure controlled pressure on the oil in said chamber to cause the oil to flow to the standpipe.

49. A method of regulating combustion in a steam boiler furnace fired with oil supplied to burners comprising, supplying oil under gravity'head to the burners from the base of a column of oil the height of which is increased in proportional relation with the fall of steam pressure in the boiler.

. 50.v A method of regulating combustion 1n a steam boiler furnace fired with oil supplied to burners comprising, maintaining a body of oil at a constant level, withdrawing oil from said body at a rate which bears an inverse proportional relation to variations in the boiler steam pressure, continuously dlscharging the oil so withdrawn into a standpipe to maintain a head of oil therein 

